我建议在array param中添加meta\\u查询，请尝试以下操作

add_shortcode( \'sc_count_brands\', \'sc_count_brands_code\' );
function sc_count_brands_code($atts) {
  $values = shortcode_atts( array(\'category\'  => \'Horology\',), $atts );
  $args = array(
    \'post_type\' => \'brands\',
    \'post_status\' => \'publish\',
    \'meta_query\' => array(
        array(
          \'key\'     => \'br_category\',
          \'value\'   => esc_attr($values[\'category\']),
          \'compare\' => \'=\'
        ),
    ),
  );
  $query = new WP_Query( $args );
  $countn = $query->found_posts;
  $buffer = \'<span class="magby">Featuring </span><span class="axiac">\' . $countn . \'</span><span class="magby"> brands</span>\';
  wp_reset_postdata();
  return $buffer;
}